1. Field of the Invention
The invention relates to an improved structure of transformer, and more particularly, to an improved structure of transformer making use of a trouser-like flap furnished by fitting to the main core part of the iron core to form the transformer's secondary winding.
2. Description of the Prior Art
Most of the transformers of the prior art are coil type transformer which employs two wires (enamel covered wire) to wind around a same iron core forming a primary winding to be connected to a power source and a secondary winding to be connected to a load. The relation for generating induction voltage depends on the secondary-to-primary-turn ratio. When it comes to changing the output voltage of the coil type transformer, at least the number of turn of the coil needs to be changed in the design of the corresponding single manufacturing process in light of each kind of transformer's specifications making it inconvenience in production, complication in the process of the winding process of the coil, relatively high in manufacturing cost, thereby resulting in uneconomical effect.
What is more, in light of the requirements of the characteristic of low voltage and high current, and since the coil of the secondary winding has to use a conduction wire (enamel covered wire) having relatively larger diameter, the gap formed between each turn of wire of the coil will be relatively larger making the fact that the volume of the overall transformer appear irrationally increase and causing the increase of eddy current loss. This is a demerit of the transformers of the prior art in application.
FIG. 1 is an isometric exploded view of the structure the transformer employing metal strips to be a secondary winding of the prior art while FIG. 2 is an outward appearance of the assembled structure the transformer of the prior art. For the sake of satisfying the requirements of constantly increasing the output current of the secondary winding, and saving the wire winding space, another transformer structure of the prior art was provided as shown in FIG. 1, and FIG. 2. The transformer structure of the prior art mainly includes a lead frame (9), two oppositely combined iron cores (7), and a plurality of thin metal strips (8), each of them with a thickness of 10 μm˜100 μm. Each of the metal strips (8) has a main core part (71) and four side wing parts (72) with side openings (74) provided in between thereof. A containing space (73), formed between the main core part (71) and the four side wing parts (72), is outwardly communicative through the four side openings (74). The lead frame (9) having a penetration hole (91) furnished at the center thereof for slipping on the main core part (71) is contained in the containing space (73) of the iron core (7). The lead frame (9) also has a bobbin furnished at the mid-section of the outer circumference thereof for the primary winding (92) (coil) to be wound with a positioning part (931) defined by upper-and-lower partitioned plates (93) that has a wire connecting seats (94) furnished at an end corner thereof and capable of stretching out of the iron core (7) through the side openings (74). At each of the wire connecting seats (94), there is at least a wire connecting posts (941) connected to the primary winding (92). Each of the metal strips (8) has a hollow part (81) that is furnished at the center thereof, and is capable of slipping on the positioning parts (931) making all of the metal strips (8) axially stack up. Moreover, each of the metal strips (8) has an opening gap (82) at a corner thereof having extended polar legs (83) capable of stretching out of the iron core (7) through the side opening (74). When it comes to assembling, a plurality of partitioning metal strips (84) are placed in between the metal strips (8) making each of the metal strip (8) form a secondary winding. This kind of stacking up metal strips (8) and partitioning metal strips (84) is capable of lowering the eddy current loss in practical application. However, it will result in having relatively larger overall induction loss.
FIG. 3 is an isometric exploded view of another structure the transformer employing metal strips to be a secondary winding of the prior art while FIG. 4 is an outward appearance of the assembled structure the transformer shown in FIG. 3 of the prior art. Further another transformer structure of the prior art was provided as shown in FIG. 3, and FIG. 4, The transformer structure of the prior art mainly includes a lead frame (90), a plurality of metal strips (80) having thickness from tens of mini meters to hundreds of mini meters, and a pair of oppositely combined E-shaped iron cores (70). The lead frame (90) has a transversely stretching penetration hole (901) with a plurality of slots (902) furnished at the periphery thereof for providing a primary winding (903) (coil). The lead frame (90) has wire connecting seats (904) formed at both ends of the penetration hole (901) where one of the wire connecting seats (904) has wire connecting posts (905) connected to both ends of the primary winding (903). The metal strips (80) being in inverse U-shape are arranged in the direction parallel to the axis of the penetration hole (901) to cover all the plurality of slots (902) at the outer circumference  the primary winding (903) may be wound around the outer circumference of the metal strips (80)  so as to form a sandwich winding and form polar legs (801) stretched in the same direction as those of the wire connecting posts (905) at both ends of the metal strips (80). When it comes to assembling, a cap (802) having an appropriate containing space (803) and a pair of side penetration holes (804) corresponding to the penetration hole (901) is employed to cover the lead frame (90) and the metal strips (80). Afterward, the pair of oppositely combined E-shaped iron cores (70) has their central main core parts stretch through both of the side penetration holes (804) respectively of the cape (802) to be contacted each other so as to form another transformer making use of the metal strips (80) to be a secondary winding. As this kind of structure having each of the metal strips (80) furnished in the direction of the main core part of the E-shaped iron cores (70) is capable of effectively diminishing induction loss. Moreover, since the metal strips (80) having the characteristic of not being bendable with structural products appeared in horizontally rather than vertically stacking up has seriously affected the diversity and competitiveness of transformer product.